/*抽象类 */
abstract class creature {
    public abstract String feature();
}

class plant extends creature {
    String leaf;

    plant(String _leaf) {
        this.leaf = _leaf;
    }

    public String feature() {
        return leaf;
    }
}

class animal extends creature {
    String mouth;

    animal(String _mouth) {
        this.mouth = _mouth;
    }

    public String feature() {
        return mouth;
    }

}

public class example3_16 {
    public static void main(String[] args) {
        plant A = new plant("leaf");
        System.out.println("plant's feature:  " + A.feature());
        animal B = new animal("mouth");
        System.out.println("animal's feature:  " + B.feature());
    }
}
// 抽象父类中的抽象函数必须在抽象子类中实现